A conventional elbow connector for a power cable has been widely disclosed and is well known as a medium connector that facilitates the connection between a power cable and a high-voltage device such as a switch or the like in a padmount.
Such an elbow connector is connected to or disconnected from, for example, a bushing insert attached to a bushing well of a switch so as to be connected to the switch via a cable.
That is, the elbow connector has a first terminal side that is provided to accommodate a power cable, and a second terminal side that is provided to accommodate an insertion end of the bushing insert.
Further, the elbow connector also has another terminal side that is provided opposite to the second terminal side to receive an insulation plug and an insulation cap, thereby forming a T-type structure along with the first and second terminal sides.
An exemplary elbow connector is disclosed in Patent Document 1.
That is, the elbow connector of Patent Document 1 includes an insulating housing that has a multi-layer structure, in which an internal insulating layer formed of a rubber-like insulating material is internally and externally surrounded by a semi-conductive protection layer formed of a rubber-like elastomer, such that a cable receiving part in a vertical direction and a bushing connection part and a voltage detection part in a horizontal direction are formed in a horizontally symmetric manner.
The elbow connector also includes a conductor that is assembled in a state of protruding in the central portion of the bushing connection part and the voltage detection part while forcedly engaging wires of a high voltage cable through an internal space of the cable receiving part and to which a stud bolt screwed onto a bushing insert attached to a switch is assembled.
Further, the elbow connector includes an insulation plug in which a fastening nut and a test point, which are screwed onto a rear end of the stud bolt, are insert-molded onto front and rear ends of an insulating material so as to be coupled to the voltage detection part, and an insulation cap that covers the test point exposed to a rear end of the insulation plug.
The cable includes an adapter assembled onto an insulation cladding in order to prevent shaking in the cable receiving part and to facilitate sealed assembly.
The elbow connector of Patent Document 1 (Korean Unexamined Patent Publication No. 10-2008-0024646 published on Mar. 19, 2008) has a function of detecting a voltage using the test point of the insulation plug so as to check an activated state of a distribution line or detecting a phase of power source side and load side and checking an open phase state thereof.
In order to eliminate the drawbacks of Patent Document 1 wherein the protruded length of the voltage detection part side is increased, a technique is disclosed in Patent Document 2 (Korean Patent Registration No. 10-1066526, registered on Sep. 15, 2011), in which an asymmetric structure is formed such that a length of the voltage detection part is made smaller than a bushing connection part, and a manipulation ring of the insulation cap is made into a folded type, thereby reducing the protruded length of the voltage detection part to the max.
Although Patent Documents 1 and 2 have a function of checking an activated state of a distribution line or detecting a phase of power source side and load side and checking an open phase state thereof, configurations of Patent Documents have a problem in that, when a cable is intended to be grounded as necessary, the configurations should have a switch having a separate ground switch therein. Further, in the case of a conventional elbow connector having no grounding function, it is first disconnected from a switch and then a separate grounding elbow connector is connected to the switch so as to check a voltage and ground itself, leading to troublesome, complex work and providing inconvenience and limitations in use.
In other words, a conventional elbow connector has drawbacks in that, since it has no grounding function, upon replacement of a cable in a switch or line working, a switch having a separate grounding switch therein should be employed, or a separate grounding connector should be connected thereto so as to check a voltage and ground itself, leading to complex replacement of a cable, increased sire of the switch, and limited range in use.
To solve these problems, the applicant proposed a ground type elbow connector disclosed in Patent Document 3 (Korean patent Registration No. 10-1368384, registered on Feb. 21, 2014) that has a grounding connection structure to allow a power cable to be grounded by the elbow connector itself and in which safe replacement or maintenance of a switch is ensured by safely checking a grounded state of a power cable using a ground inspection connection device.
The elbow connector of Patent Document 3 is separately provided with the ground inspection connection device that has a function of detecting an electric charge.
Thus, Patent Document 3 has the same problem as those of Patent Documents 1 and 2, in that, although a grounding operation is instantly performed, the ground inspection connection device having a function of detecting an electric charge is separately provided, resulting in an unreliable, unstable connection of the ground inspection connection device, which may possibly cause a safety accident or malfunction.
Furthermore, there have also been other problems such as separate storage, inconvenient portability in use, sensor damage due to careless handling, or the like of the ground inspection connection device.